Heating furnace



Febv 7, W50 F. o. HESS 2,496,914

HEATING FURNACE Filed Sept. 26, 1946 2 Sheets-Sheet l INVENTOR.

' Feb. 3/, 1950 F. o. HESS 96,914

- HEATING FURNACE Filed Sept. 26, 1946 2 Sheets-Sheet 2 MATTOW/VE)Patented 7, 1950 UNITED STATES PATENT OFFICE HEATING FURNACE Frederic 0.Hess, Philadelphia, Pa., assignor to Selas Corporation of America,Philadelphia, Pa., a corporation of Pennsylvania Application September26, 1946, Serial No. 699,417

8 Claims.

This invention relates to heating furnaces and is especially concernedwith such furnaces in which work pieces and articles of elongatedextent, such as tubing, bars, rods and the like, are transportedlengthwise through the furnace for progressively heating work pieces ina controlled manner to a desired elevated temperature.

It has already been proposed to heat work pieces or stock of elongatedextent by moving the Work in single line transit and in endlessprocession through one or more furnace units for progressively heatingsuccessive longitudinal portions of the work to a high temperature. Whenit is desired to heat wc'k rapidly in single line transit, the furnaceunit or units are preferably of a type in which a high thermal head isproduced by an immense heat release closely fitting about the travellingwork pieces.

When the heating furnace comprises a number of furnace units, such unitsare in end to end relation and relatively close together. With such anarrangement the heated furnace gases discharged through the exit andentrance openings of adjacent furnace units form a high temperaturegaseous atmosphere which blankets the Work and protects the latter whilesuccessive portions of the work pass from one furnace unit to asucceeding furnace unit. In this manner work or stock of elongatedextent can be heated at such rates that a considerable weight of stockcan be handled in single line transit at a relatively high rate of speedthrough one or more such furnace units.

In many heating operations where it is desired to heat work of elongatedextent in single line transit, the speed at which the work must be movedis so high that a heating furnace of prohibitive length is required toaccomplish the requisite heat treatment. In other words, while it ispossible to construct a single heating furnace or a number of furnaceunits in end to end relation to heat treat work in single line transitto take care of exceptionally rapid speeds at which the work mustsometimes be moved, such heating furnaces or furnace units often arecostly and expensive and require an unduly large amount of plant space.

In accordance with this invention, an improved heating furnace isprovided with embodies all of the desirable qualities of heatingfurnaces now employed for heating elongated work or stock in single linetransit, such improved furnace not only being considerably smaller insize compared to existing heating furnaces of comparable capacity, butalso capable of heating 2 work or stock in single line transit at higherspeeds than heretofore possible. The principles of the invention may beembodied in a, single heating furnace or a number of furnace units inend to end relation, and in either case the actual time during whichwork is under heat treatment is relatively short compared to batchheating of Work and the deleterious effects of time-at-temperature, suchas scaling and decarburiz'ation, are minimized.

This is accomplished by providing mechanism for supporting a number ofelongated work pieces alongside of each other and transporting andadvancing such work pieces in a battery lengthwise through a heatingfurnace which may comprise a single unit or a number of units in end toend relation. The work pieces are fed lengthwise in single line transitand in rapid succession to a first region of the heating furnace wherethe transporting mechanism is effective to advance the work pieces; andthe heated work pieces are discharged lengthwise in rapid succession andleave the transporting mechanism at a second region of the heatingfurnace which is laterally removed from the first region at which'theincoming Work pieces are received. While the battery of work pieces isbeing advanced lengthwise through the heating furnace by thetransporting mechanism, the work pieces are bodily shifted sideways inone or more steps from the incoming first region, whereby successivework pieces will be at the second region when ready to be dischargedfrom the heating furnace.

In the heating furnace of the invention the elongated Work pieces areheated for substantially the same interval of time during movementthrough the furnace, whereby substantially uniform heating of successivelongitudinal portions of all work pieces to the same elevatedtemperature is automatically effected. Further, the work pieces can befed lengthwise to and removed lengthwise from the heating furnace atexceptionally high rates of speed while the work pieces in the heatingfurnace can be transported lengthwise at a considerably slower speed. Bybeing able to move the work pieces at a considerably slower rate in theheating furnace while equipment but also providing such equipment whichwill ocupy a minimum amount of space.

The invention, together with the objects and advantages thereof will bemore fully understood upon reference to the following description takenin conjunction with the accompanying drawings forming a part of thisspecification, and of which:

Fig. 1 is a top plan view more or less diagrammatically illustrating anumber of furnace units embodying the invention, such furnace units being arranged relatively close together in end to end relation for workor stock of elongated 'extent to pass lengthwise therethrough to effectthe desired heating of the work{ Fig. 2 is an enlarged fragmentary sideelevation of the furnace units shown in Fig. l to illustrate moreclearly details of the mechanism disposed between adjacent furnace unitsfor sup porting and transporting the work or stock therethrough;

Fig. 3 is an enlarged fragmentary vertical sectiona1 view of the ends ofadjacent furnace units shown in Figs. 1 and 2 to illustrate the invention more clearly;

Fig. 4 is a transverse sectional view taken at line 4-4 of Fig. 3;

Figs. 5 and 6 are fragmentary transverse sectional viewssimilar to Fig.4to illustrate more clearly the mechanism for shifting the work or stocksideways within the furnaces; and

Fig. 7 is a sectional view more or less diagrammatically illustratingthe type of roller disposed between each pair of adjacent furnace unitsfor transporting the work or stock lengthwise through the furnaces.

Referring to Figs. 1 to 3 inclusive, 1 have shown my inventionas'applied to a heating furnace comprisin a number of furnace units II!which are relatively close together in end to end relation and throughwhich work or stock II, such as bars or tubes and the like, for example,of elongated extent is transported for heating successive longitudinalportions'thereof to a desired elevated temperature. As best shown inFig. 3, the furnace units ID are provided with refractory'lined chambersI2 which are relatively small in transverse section and formed withelongated aligned openings I4 and I5. in the end walls through which thework II enters and leaves each chamber. To produce a high rate ofhatliberation in as small a space as possible, a number of burners I6are crowded and incorporated in'the opposing side walls of each chamberI2.

The refractory walls I1 defining the chambers I2 are formed of suitablerefractory material capable of withstanding the high temperatureSprQ-duced in the chambers. The refractory walls I! are encased in outermetallic shells I8 adapted to be supported in any suitable manner. Theouter shells I8 may include hollow end sections I9. through which acooling medium, such as water, for example, is circulated (not shown) toeffect cooling and prevent undesirable overheating of the end walls.

As best shown in Fig. 4, suitable connections are provided forindividually supplying a combus tible fuel mixture to each burner I6.The cornbustible fuel mixture may be delivered from a source of supplyto manifolds 2i! to which are connected conduits 2I communicating withthe burners I6. Suitable controls, including valves 22 connected in theconduits 2| be provided to control the pressure and rat at which thecombus- 4 tible fuel mixture is individually supplied to each burner I6.

The burners I6 preferably are of a direct fired type capable ofproducing high heating temperatures in the chambers I2. Although not tobe limited thereto, burners which have been found especially suitableare of the kind described and illustrated in Hess Patent No. 2,215,079,granted on September 17, 1940, and, if desired, reference may be hadthereto for a detailed description of the burner structure.

In compact furnace units of the kind just described, the work or stockII is heated rapidly by the heating effects produced within the chambersI2. Such heating effects include both radiant and convection heatingcomponents. When high temperature heating effects are required to heatsuccessive longitudinal portions of the work II rapidly to the desiredelevated temperature, the high temperature products of combustion orfurnace gases whip through the furnace chambers I2 at a relatively highvelocity. Such furnace gases pass through the openings I4 and I5 andproduce what is often referred to as a sting out; that is, a gaseousatmosphere is roduced which envelops the work as it passes from onefurnace to the next succeeding furnace.

The work pieces II, which are of longer length than the individualfurnace units ID, are transported through the furnaces If! by conveyorrollers 23 disposed in the gaps between adjacent furnaces. As best shownin Fig. 7, the rollers 23 are hollow and formed with a number of grooves24 adjacent to one another for simultaneously moving a battery ofelongated work pieces at the same time through the furnace units 20. Theends of the rollers 23 are fixed to hollow stub shafts 25 journaled inbearings 26 provided at the upper ends of standards 27 which aresupported in any suitable manner between adjacent furnace units IIl.Rotary union connections 28 are provided at the ends of the shafts 25 towhich flexible conduits 29 are connected for circulating a coolant, suchas water, for example, through the hollow shafts 25 and rollers 23 fixedthereto.

The rollers 23 may be driven in any suitable manner. As shown in Figs. 2and 4;, the rollers 23 may be driven by endless chains 30 connected togears 3| and 32 fixed to the shafts 25 and to shafts 33, respectively,the latter being journaled in brackets 34 extending downwardly from theends of the furnaces Ill. The shafts 33 are provided with gears 35 whichare interconnected by endless chains 36, as shown in Figs. 2 and 4, andmay be driven by a single electric motor (not shown).

In accordance with this invention the elongated work pieces II aresupported alongside. of each other by the rollers 23 and advancedlengthwise through the furnace units I f! as a unitary group. As bestshown in Fig. 1, the work pieces II are fed lengthwise in single linetransit and in rapid succession to a first region 3! of the furnaceunits ID by suitable conveyor rolls including, for example, a pair ofpinch rolls 38 disposed adjacent the entrance opening of the firstfurnace unit. The pinch rolls 38 may be driven in any suitable mannerfor positively feeding each work piece I I over the set of end grooves24 in the rollers 23 which are in alignment with the pinch rolls 38.

Since the pinch rolls 38 are usually driven at a speed which isconsiderably faster, than the rollers 23, the work pieces I I positivelyfed into the furnace units ID by the pinch rolls 38, will frictionallyslide over the set of end grooves 24 in the rollers 23 until each workpiece leaves the pinch rolls. When this occurs, the rollers 23 thenbecome effective to transport and advance each work piece I I initiallymoved into the end grooves 24 thereof.

The heated work pieces II are discharged lengthwise in rapid successionand leave the rollers 23 at a second region, indicated at 39 in Fig. 1,which is laterally removed from the first region 31 at which theincoming work pieces are received. At the second region 39 each workpiece II is advanced lengthwise in the opposite set of end grooves 24 ofthe rollers 23. When each work piece I I at the second region 39 isadvanced sufficiently for the forward end thereof to be gripped bysuitable conveyor rolls including, for example, a pair of pinch rolls'40adjacent the exit end of the final furnace unit III, such pinch rollswill be effective to withdraw the work pieces rapidly from the furnaceunits Ill. The pinch rolls 4D become effective to transport the workpieces I'I about to be discharged from th furnace units It because suchpinch rolls are driven at a higher speed than the rollers 23 andsubstantially at the same speed as the pinch rolls 38.

While the work pieces II are being advanced as a battery through thefurnace units I by the rollers 23, the work pieces are bodily shiftedsideways in a number of steps from the incoming first region 31. In theembodiment illustrated this is accomplished by providing suitable worktransfer mechanisms M in the aps between adjacent ends of furnace unitsI0. As best shown in Figs. 3 to 6 inclusive, each work transfermechanism 4| comprises a cradle 42 having teeth 43 at the top edgethereof of substantially the sam size as the grooves 24 in the rollers23. The cradle 42 in each gap between adjacent ends of furnace units I0is positioned closely adjacent to and at oneside of a conveyor roller23.

The cradles 42 at the bottom parts thereof are formed with spaced apartside walls 44 which are substantially parallel and extend downwardlyfrom the top toothed portions 43, as shown in Fig. 3. As seen in Figs. 4to 6 inclusive, the side walls 44 are formed with aligned notches toprovide three spaced apart legs 45, 46 and 41.

In the spaces between the spaced apart side walls 44 of each cradle 42are positioned a pair of disks 48 and 49 of substantial thickness. Thedisks 48 and 49 are fixed to shafts 50 and respectively. As best shownin Figs. 3 and 4, each shaft 59 is journaled at its ends in bearings 52which may be removably secured to theopposing ends of adjacent furnaceunits III. The shafts 50 may be driven in any suitable manner and, asshown, are driven from the shafts 33 through gearing indicated at 53 and54. The shafts 5| may be journaled at their ends in the same manner asas the shafts 50 and chain driven therefrom, as indicated at 55.

To the disks 48 and 49, adjacent to the peripheral edges thereof, arefixed pins 56 and 51, respectively. As shown in Figs. 4 and 6, thedistances between the shafts 5B and 5| and the pins 55 and 51,respectively, are substantially the same as the distances between thelegs 45 and 46 and the legs 46a'nd '41 of the cradle 42. The pins 56 and5'! project outwardly from the opposing faces of the disks 48 and 49 andengage and bear against the closed ends of the notches formed in thespaced apart side walls 44; The operation of the work transfermechanisms 4I- just. described is as follows, it being under-' stoodthat the several transfer mechanisms are adjusted so that they alloperate in unison to shift the work pieces I] laterally in a number ofsteps from the region 37 to the region 39 in the furnace units III. InFig. 4 the cradle 42 is in a first intermediate position at which timethe cradle is supported at the closed ends of the notches'by both thepins 56 and 51 and also the shafts 50 and 5|. In such first intermediateposition of the cradle 42, the teeth 43 at the top edge thereof arebelow the grooves 24 in the roller 23 adjacent thereto and cannotinterfere with the lengthwise movement of the work pieces II in thefurnace-units III.

The disks 48 and 49 as seen in Fig. 4 rotate about the shafts 50 and SIin a clockwise direction. When the disks 48 and 49 rotate from theposition shown in Fig. 4 to that shown in Fig. 5, the cradle is raisedby the pins 56 and 5'! from its first intermediate position to itsraised position. In moving to the raised position shown in Fig. 5, theteeth 43 at the top edge of the cradle 42 are moved upwardly to a heightor level above the rollers 23 adjacent thereto. As the teeth 43 at thetop edges of the several cradles 42 move up in unison, therefore, thework pieces in the grooves 24 of the rollers 23 are picked up by theteeth 43 and lifted off the rollers.

When the disks 48 and 49 rotate 90 from the raised position shown inFig. 5 to a second intermediate position shown in Fig. 6, the workpieces II are shifted laterally of the furnace units I0 from one set ofaligned grooves in the rollers 23 to an adjacent set of aligned groovestherein. In moving to the second intermediate position shown in Fig. 6,the teeth 43 pass below the grooves 24 in the rollers 23, so that thework pieces I I are again supported by the rollers and advancedlengthwise by the latter through the furnace units It.

From the second intermediate position shown in Fig. 6 the disks 48 and49 continue to rotate in a clockwise direction. After rotating fromthesecond intermediate position in Fig. 6, the disks 48 and 49 return tothe first intermediate position shown in Fig. 4 after passing through alower position which has not been illustrated. From such firstintermediate position of the disks 48 and 49; the operation of the worktransfer mechanism is repeated in the manner just described, whereby thework pieces II are bodily shifted in a number of steps from one set ofaligned grooves 24 to an adjacent set of aligned grooves in the rollers23.

In view of the foregoing, it will now be understood that an improvedheating furnace has been provided in which elongated work pieces can berapidly fed lengthwise to and rapidly removed lengthwise from theheating furnace while the work pieces in the heating furnace can betransported lengthwise at a considerably slower speed. In the embodimentof the invention shown and just described, five furnace units it areprovided in end to end relation, as seen in Fig. 1. The elongated workpieces I I are of such length that, when the work pieces are fed insuccession into the furnace units III at the incoming region 31, eachwork piece extends from the entrance opening of the first furnace unitIll approximately to the exit end of the fourth furnace unit Ill. Thus,in the length of time each work piece I I is in the heating furnaceshown, it is advanced lengthwise therethrough a distance approximatelyequal 'tothe length of one furnace unit III plus.

th see distan bet een the f urt an iine fu n e u t 10, bef re he fo ware d thereo ea hes a osi on whe it will be ri ed by the pi h ol e s 4n.

.n v ncin th gh the he tin furnaee, c o k ece is bodil hifted in fivesteps f o the nd r ov s 2 the rollers .23 at the region 3 o e oppositeend roo s 4 at the re on D in the in va s 9f ime in which he wo a sf mchan sm 4! shi s he wor pieces I I d ay om ne se of a i ned ooves 24 toon a ac se o aligned roo es n t e er 3, e o k p eces momentari y are notmoved lengthwise through the heating furnace. However, as soon as theshifting and transferring of he work p e H is com leted b th work n e ma ism, t e onve or olle s be co e ive to a n e and trans ort-the ork pic s l thw se from the in et to the out t of th he t lui' e T us, w ile te w rk i s I are moved leng i e more or less continuu v n e e pro s tothe heatin fu nace and le ve h e ing nac in h same nor, the forwardadvance of the Work pieces he a n n e s in ermi ent a act r- By a of amand w thout limi ati n, t e elongated work pieces I I may be fed singleline tr n t to the heatingfui'n oe a d eav th h a ing furnace in asimilar manner at a speed of bou 300 ee e minute wh le the o p e mayadvan e engthwi e in he u hee at an e e t spee of out t pe minute to cmp sh the s ed hea treating o he work. It will readily be apparent thatif a heating furnace were provided to accomplish the identical heattreatment of the work in whichthe Work pieces pass in single linetransit at a speed of b u 0 feet r mi u a h at ng furnace o undu y longl t ld e necessa It should be noted that each work piece II will passthrough the heating furnace shown in approximately the same interval oftime so that successive longitudinal portions of each work piece will beheated substantially to the same .eleivetted mper t re- Thus dur ng themovemen o the work p ce ll t rou h he furnace units I 1;, differentlongitudinal portions of the work p eces wil be u e d t the high t merature ea i f e ts n e u -hos cham ers I2 for app o im te e s me o eall leng h o t me; a d w so be as g h ugh the gaps between the ends ofadjacent furnace units II] for approx.- imately the same overall lengthof time. While the o k s pass n h gh the a s betwe n th ends of adjacentfurnace units II], the portions thereof he a s a e en eloped by atmosp es of h d furnac ases di char ed from h t ance nd ex p i gs 4 a d I5, asp evio s y p a ned t eby p ec i g t e wo k a d p ev n u i ab e coo i a doxid t onsuiteble sp chan e m chani m, (not s n o a y well known ype m ybe p ovided for the driving means for the disks 48 and .49, whereby thelatter will be rotated at the desired speed to shift the work pieces I Isideways on theconveyor rollers 23. Further, by providing such speed hame ha sm ch i ope ble to d s h nect the disks 48 and 49 from the drivingmeans therefor. t e di ks may e s op d at os t on at which the cradles42 will be below the conveyor rollers 23 and not interfere with thetransport of the work pieces II by the latter. In this maner all o e w rp e s an e move ou o the furnace units I!) when this becomes necessary.If desired, provision may begmade for re- VtISih the rotation of theshafts 33 whereby the work pieces can be moved backward as a group henthe work ransfer me ha isms 4| are r nderc inoperable and it shouldbecome necessary to move all of the work pieces out of the heatingfurnace. The parts of the work transfer mechanism H adjacent the exitopenin s I5, and in the path of movement of the heated furnace gasesdischarged therefrom, may be formed of any Well known high temperaturealloy.

The heating furnace illustrated is extremely flexible and may beemployed for heating work pieces of different sizes. Thus, when workpieces which are of less weight per unit length are heat treated in theheating furnace shown and the work pieces may pass through the heatingfur nace in a shorter length of time, the pinch rollers 55 at the exitopening of the final furnace unit Ill can be shifted so that the workpieces will be gripped by such pinch rollers after the work has beenshifted sideways a number of steps less than the maximum number of stepsprovided for the heating furnace.

In heat treating metallic work, such as steel,

copper, brass and the like, for example, the number of furnace units IIIrequired in each particular case will depend, of course, upon the weightper unit length of the Work and the composition of the work as well asthe elevated temperature to which the work must be heated to impartthereto the desired metallurgical characteristics. Further, the numberof furnace units I0 necessary and the number of steps in which the workpieces are bodily moved sideways from the incoming region 3'! to theoutgoing region 39 will depend upon additional factors, such as, forexample, the speed at which the work pieces are fed in single linetransit to the heating furnace and conveyed therefrom in a similarmanner.

Although I have shown and described a particular embodiment of theinvention, it will be apparent to those skilled in the art thatmodifications and changes may be made without departing from the spiritand scope of the invention.

I therefore aim to cover all modifications and changes which come withinthe spirit and scope of the invention, as pointed out in the followingclaims.

What is claimed is:

l. A heating apparatus comprising a number of axially aligned separateunits in end to end relation and'having entrancevand exit openings forpassage of a number of work pieces therethrough alongside of each other,conveyor mechanism iin the space between said units for supporting andtransporting the work pieces through the units, on pa o sa d con yo mechism being a ranged to receive incoming work pieces and anhe pe t thereola ra ly o se it respect t aid one part being an e to di ar e h atedwork pieces, and transfer mechanism for shifting he o k i es latera y nsa d c e m ch during transport through and between said units to movethe work pieces from said one part to said other part of the conveyormechanism.

2, A heating apparatus comprising a number of units in end to endrelation and having entrance and exit openings for passage of a numberof work pieces of elongated extent therethrough alongside of each other,conveyor mechanism ineluding rolls between the units for supporting andtransporting work pieces through the units, and including work transfermechanisms between the units for bodily shifting the work 9 piecessideways during transport through the units.

3. Heating apparatus comprising a number of furnace units in end to endrelation and having entrance and exit openings for passage therethroughof a number of elongated articles of greater length than each furanceunit, conveyor mechanism including hollow rolls between the furnaceunits for supporting and transporting the elongated articles through thefurnace units, said hollow rolls having inlets and outlets forcirculating a coolant therethrough, and means comprising work transfermechanisms including parts disposed between the furnace units adjacentto the hollow rolls for bodily shifting the elongated articles sidewaysduring transport through the furnace units.

4. Heating apparatus comprising a number of furnace units in end to endrelation and having entrance and exit openings for passage therethroughof elongated articles of greater length than each furnace unit, meansfor firing said furnace units to an elevated temperature, conveyormechanism including multi-grooved rolls between the furnace units forsupporting and transporting the elongated articles through the furnaceunits, and means including article transfer mechanisms for raising andbodily shifting the elongated articles from one set of aligned groovesto another set of aligned grooves in the rolls during transport throughthe furnace units.

5. Heating apparatus comprising a number of furnace units in end to endrelation and having entrance and exit openings for passage therethroughof elongated articles of greater length than each furnace unit, meansfor firing said furnace units to an elevated temperature, conveyormechanism including .multi-grooved rolls between the furnace units forsupporting and transporting the elongated articles through the furnaceunits, and article transfer means including movable toothed elementsbetween the furnace units operable to intermittently interfere with thetransport of the elongated articles by said rolls and to shift thearticles from one set of aligned grooves to another set of alignedgrooves in said rolls.

6. Heating apparatus comprising a number of furnace units in end to endrelation and having entrance and exit openings for passage therethroughof elongated articles of greater length than each furnace unit, conveyormechanism including multi-grooved rolls between the furnace units forsupporting and transporting the elongated articles through the furnaceunits, means for feeding the elongated articles lengthwise in successionto a first set of aligned grooves in said rolls, means for removing theelongated articles lengthwise in succession from a second set of alignedgrooves in said rolls, and article transfer mechanism operableintermittently to interfere with the transport of the elongated articlesby said rolls and shift the articles in one or more steps from saidfirst set of aligned grooves to said second set of aligned groovesduring transport of the articles through the furnace units.

'7. A heating apparatus comprising a number of units in end to endrelation and having entrance and exit openings for passage therethroughof elongated articles of greater length than each unit, means for firingeach unit to an elevated temperature, conveyor mechanism including rollsbetween the units for supporting and transporting the elongated articlesthrough the units, means for feeding the elongated articles lengthwisein succession onto one region of said rolls, means for discharging theelongated articles lengthwise in succession from a second region of therolls, and means for bodily shifting the elongated articles sideways onsaid rolls from said first region to said second region duringlengthwise transport through said units.

8. Heating apparatus comprising a number of furnace units in end to endrelation and having entrance and exit openings for passage therethroughof elongated articles of greater length than each furnace unit, meansfor firing each furnace unit to an elevated temperature, conveyormechanism including rolls between the furnace units for supporting andtransporting the elongated articles through the furnace units, meansincluding pinch rolls adjacent to the entrance opening of the initialheating furnace unit for feeding articles lengthwise in succession ontoa first region of said rolls, means including pinch rolls adjacent tothe exit opening of the final furnace unit for discharging the elongatedarticles lengthwise in succession from a second region of the rolls, andmeans for bodily shifting the elongated articles sideways on said rollsfrom said first region to said second region during lengthwise transportthrough said furnace units.

FREDERIC O. HESS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 699,130 Allis May 6, 1902 704,286Allis July 8, 1902 720,904 Edwards Feb. 1'7, 1903 863,841 George Aug.20, 1907 2,326,843 Ely Aug. 17, 1943 2,451,053 Anderson et al. Oct. 12,1948

